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BMJ's Evidence-Based Journals aim to alert clinicians to important
advances in specific areas of study:
- for Evidence-based Medicine, this includes internal medicine,
general and family practice, surgery, psychiatry, paediatrics, and
obstetrics and gynaecology.
- for Evidence-Based Mental Health this includes treatment,
diagnosis, aetiology, prognosis, continuing education, economic
evaluation, and qualitative research in mental health.
- for Evidence-Based Nursing the purpose is to identify, using
predefined criteria, the best quantitative and qualitative
original and review articles on the meaning, cause, course,
assessment, prevention, treatment, or economics of health problems
managed by nurses and on quality assurance.
Each hard-copy issue of the Evidence-Based Journals begins with a
section entitled 'Purpose and Procedure' which describes in detail
that journal's philosophy and the criteria for inclusion. In the
online guide to EBMJ, this description from each journal is included
in full.
1 EBMJ
AN - Accession number & update
B2ND5C 20031106.
TI - Title
Lewington S, Clarke R, Qizilbash N, et al, for the Prospective
Studies Collaboration. Age-specific relevance of usual blood
pressure to vascular mortality: a meta-analysis of individual
data for one million adults in 61 prospective studies.
SO - Source
Lancet, 2002, vol. 360, p. 1903-13.
AU - Author(s)
Lewington-S, Clarke-R, Qizilbash-N, et-al, for-the-
Prospective-Studies-Collaboration.
BI - BMJ title
Review: usual blood pressure is directly related to vascular
mortality throughout middle and old age.
BS - BMJ source
Evidence Based Medicine, Jul, 2003, vol. 8, no. 4, p. 122.
EV - Evaluation
QUESTION: In adults with no history of vascular disease, what
is the age specific association between usual blood pressure
and vascular mortality?
Data sources:
Studies were identified through searches of Medline and
EMBASE/Excerpta Medica, hand searches of meeting extracts, and
discussions with investigators.
Study selection:
Prospective observational studies were included that reported
data on blood pressure at baseline and cause and date of
death. Studies that deliberately recruited patients with a
history of stroke or heart disease were excluded.
Data extraction:
Reviewers contacted investigators of selected studies to
obtain individual patient data. People with a history of
stroke or heart disease at baseline were excluded from the
analysis. Individual data were used to estimate the main risk
factor of interest: usual (i.e., long term) blood pressure.
Meta-analysis was used to relate mortality during each decade
of death to the estimated usual blood pressure at the start of
that decade; analyses were corrected for time dependent
regression dilution.
Main results:
Individual patient data for 958 074 people (12.7 million
person years of follow up) in 61 studies were included. 11 960
people died from stroke, 34 283 died from ischaemic heart
disease, and 10 092 died from other vascular causes. The age
specific associations between usual blood pressure and
vascular mortality are shown in the table. For all ages of
death between 40 and 89 years, a lower usual systolic or
diastolic blood pressure was associated with a lower risk of
vascular death. The association was less extreme at older ages
than at younger ages.
Conclusion:
In people with no history of vascular disease, usual blood
pressure is directly related to vascular mortality throughout
middle and old age, even at pressures as low as 115/75 mm Hg.
Associations between blood pressure (BP) and vascular
mortality*
Cause of death Age HR for HR for
at risk relation relation
(years) with SBP* with DBP*
Stroke 40-49 0.36 (0.32 to 0.35 (0.30 to
0.40) 0.40)
50-59 0.38 (0.35 to 0.34 (0.32 to
0.40) 0.37)
60-69 0.43 (0.41 to 0.40 (0.38 to
0.45) 0.42)
70-79 0.50 (0.48 to 0.48 (0.45 to
0.52) 0.51)
80-89 0.67 (0.63 to 0.63 (0.58 to
0.71) 0.69)
Ischaemic heart 40-49 0.49 (0.45 to 0.47 (0.43 to
disease 0.53) 0.51)
50-59 0.50 (0.49 to 0.52 (0.50 to
0.52) 0.55)
60-69 0.54 (0.53 to 0.56 (0.54 to
0.55) 0.58)
70-79 0.60 (0.58 to 0.62 (0.60 to
0.61) 0.64)
80-89 0.67 (0.64 to 0.70 (0.65 to
0.70) 0.74)
Other vascular 40-49 0.43 (0.38 to 0.43 (0.37 to
causes 0.48) 0.50)
50-59 0.50 (0.47 to 0.48 (0.44 to
0.54) 0.52)
60-69 0.53 (0.51 to 0.49 (0.46 to
0.56) 0.53)
70-79 0.64 (0.61 to 0.61 (0.57 to
0.67) 0.66)
80-89 0.70 (0.65 to 0.71 (0.64 to
0.75) 0.79)
*DPB = diastolic blood pressure; HR = hazard ratio;
SBP = systolic blood pressure.
*The HRs reflect an association between 20 mm Hg lower usual
SBP (throughout range down to 115 mm Hg) and 10 mm Hg lower
usual DBP (>=75 mm Hg) at the start of the decade.
Commentary
The study by Lewington et al is unique in estimating long term
blood pressure and its associations with vascular mortality
for an extremely large number of people. It relies on a
statistical technique to correct for regression dilution bias.
What is regression dilution bias?
Let's take an example of a study to assess the risk of lung
cancer over 20 years among people who say they smoke compared
with non-smokers. At baseline, it is likely that some people
who report not smoking do in fact smoke and vice versa. In
addition, over the follow up period, people will stop and
start smoking. For simplicity, let's say the true effect of
long term smoking is to increase the risk of lung cancer
tenfold. In our study, we will actually measure the risk of
lung cancer among people, most of whom smoked for some of the
20 years, and compare this with the risk among people, most of
whom did not smoke for some of the 20 years. The inaccurate
measurement of exposure to smoking has made our 2 comparison
groups more similar to each other. The observed risk among our
smoking" group is likely to be considerably less than 10 times
the risk among our "non-smokers". We have "diluted" our
comparison groups, leading to bias in the estimate of the
regression slope between our exposure (smoking) and our
outcome (lung cancer) - hence the name "regression dilution
bias".
Blood pressure fluctuates with time. Analyses based on a
single baseline reading will tend to underestimate the effect
of blood pressure on subsequent health outcomes. One way to
overcome this regression dilution bias is to base our analyses
on participants' "usual" or long term average blood pressure.
A proportion of people included in this meta-analysis had
repeated blood pressure measurements over time, allowing the
authors to estimate people's "usual" blood pressure, and thus
correct for regression dilution bias. This correction itself
is an inexact process. However, the rigorous methods used
should have ensured that this review provided the most
accurate estimates to date of the effects of blood pressure on
subsequent health outcomes. From 40-89 years of age, and for
blood pressure > 155/75 mm Hg, the risk of vascular mortality
is clearly increased for any increment in systolic or
diastolic blood pressure.
Liam Smeeth, MBChB
London School of Hygiene & Tropical Medicine
London, UK.
DE - Descriptors
blood-pressure; cardiovascular-diseases.
YR - Publication year
2003.
PT - Publication type
Article.
AT - Article type
Aetiology.
OC - Occurrences
BMJ source (1).
LE - Length
8,235 Characters, approximately 5 PC screens.
CP - Copyright statement
Copyright 2003 by the ACP-ASIM and BMJ Publishing Group for
Evidence-Based Medicine and by the ACP-ASIM for portions
reproduced from ACP Journal Club.
2 EBMJ
AN - Accession number & update
CV2WMM 20031106.
TI - Title
Young B, Fitch GE, Dixon-Woods M, et al. Parents' accounts of
wheeze and asthma related symptoms: a qualitative study.
SO - Source
Arch-Dis-Child, 2002, vol. 87, p. 131-4.
AU - Author(s)
Young-B, Fitch-GE, Dixon-Woods-M, et-al.
IN - Author affiliation
Dr B Young, Department of Psychology, University of Hull,
Hull, UK. B.Young@hull.ac.uk.
FO - Funding organisation
Source of funding: no external funding.
BI - BMJ title
Parents' accounts of their children's respiratory symptoms
showed a Range of interpretations.
BS- BMJ source
Evidence Based Nursing, Apr, 2003, vol. 6, no. 2, p. 59.
EV - Evaluation
QUESTION: How do parents recognise and make judgments about
respiratory signs and symptoms in their young children?
Design:
Qualitative study using semi structured interviews.
Setting:
Leicester, UK.
Participants:
Parents of 19 children who were 1-6 years of age (eleven 1-3
y, eight 4-5 y; 12 boys) and were recruited from the cohort
that had completed the Child Cohort Respiratory Symptoms
Survey or attended one general practice in Leicester. The
sample included parents who had never reported wheeze in their
children and parents who had reported it, and also included
families across a spectrum of social and cultural status.
Interviews were done in the families' homes with the father
alone (n=2), the mother alone (n=14), and the mother and
father (n=3).
Methods:
The interviews were guided by a prompt list, audiotaped, and
Transcribed verbatim. Interview transcripts were analysed
using the constant comparative method. Codes were applied, and
the data were organised into thematic categories. Data were
collected until theoretical saturation occurred.
Main findings:
13 families reported previous or current history of wheeze in
their children, and 6 families reported no wheeze. Parents
described the sound of wheeze with such words as crackly,
squeaky, strangled, gasping, rasp, rattle, lisp, animal
sounding, and air noise. High pitched or whistling were the
most common words used. Some parents used words to describe
features that were felt rather than heard, such as strangled
or gasping. Some also referred to changes in a child's
appearance, chest movements, and vibrations felt when holding
the child. When asked what the term "attacks of wheezing"
meant, parents gave a range of interpretations from an episode
with sudden onset to prolonged or severe episodes. Some
parents considered every episode of wheeze as an attack.
Several parents had not witnessed shortness of breath in their
children. Most described shortness of breath as a change in
their child's breathing (labouring to breathe), appearance
(change in complexion or looking "panicky" or "worn out"), and
changes in behaviour (activity taking place at the time), with
children having to stop or "slow down".
Parents distinguished among different types of cough and
described 4 Main features: dryness or wetness, depth,
repetitiveness or persistence, and ticklishness. Several
parents distinguished between an "asthma cough" and other
types of cough.
Parents relied mostly on their own intimate knowledge of what
was normal for their children in making judgments about their
respiratory symptoms.
Conclusions:
Parents showed variability in interpreting respiratory signs
and Symptoms in their young children. Many parents applied
meanings to terms that differ from what is meant in clinical
settings.
Footnotes:
For correspondence: Dr B Young, Department of Psychology,
University of Hull, Hull, UK. B.Young@hull.ac.uk.
Commentary
Parents have an important role in assessing their children's
symptoms, But care is required in phrasing the questions put
to parents and interpreting the information they provide. It
is known that such routinely used terms as "wheeze" can have
different meanings for parents and professionals.1
In the study by Young et al, symptoms were interpreted in
several ways by a group of parents of young children.
Parents' assessments were based on observation of all aspects
of their children rather than isolated symptoms. For example,
they referred to appearance and other sensations as well as to
the sound of breathing when describing "wheeze". Parents'
assessments of symptoms drew on experiential knowledge of
children and previous occurrences of symptoms. The absence of
other symptoms was also considered in assessing whether or not
a cough was indicative of asthma.
Assessment of "shortness of breath" highlighted the difficulty
of proxy assessment of symptoms that are experienced rather
than seen. Parents referred to changes in breathing,
appearance, and behaviour to describe shortness of breath.
They were therefore describing the outward signs rather than
the child's own experience of shortness of breath. This
suggests that parents should be asked about observable signs
of symptoms rather than internal feelings experienced by
children.
Clinical implications of the study include the importance of
Recognizing that parents' assessment of symptoms can be
influenced by contextual factors, by a wider range of
sensations than health professionals would use to assess some
symptoms, and that parental assessment depends upon
observation to describe young children's experience of
symptoms. The study emphasises the importance of checking the
interpretation of apparently straightforward terms such as
"wheeze", "attacks of wheeze", "cough", and "shortness of
breath".
There are also implications for the design of valid
questionnaires in assessing symptoms in childhood respiratory
disease. The findings are important because patients and
carers are increasingly recognised as having expertise that
can contribute to self management of chronic illness.2
Peter Callery, RGN, RSCN, PhD
Senior Lecturer
School of Nursing, Midwifery and Health Visiting
University of Manchester
Manchester, UK.
CR -Cited references
1 Cane RS, Ranganathan SC, McKenzie SA. What do parents of
wheezy children understand by "wheeze"?, Arch-Dis-Child, 2000,
vol. 82, p. 327-32;
2 The expert patient: a new approach to chronic disease
management for the 21st century. London: Department of Health,
September 2001.
DE - Descriptors
attitude-to-health; asthma; parents.
YR - Publication year
2003.
PT - Publication type
Article.
AT - Article type
Qualitative.
OC - Occurrences
Author affiliation (1)
Funding organisation (1)
LE - Length
7,106 Characters, approximately 4 PC screens.
CP - Copyright statement
Copyright 2003 by the ACP-ASIM and BMJ Publishing Group for
Evidence-Based Medicine and by the ACP-ASIM for portions
reproduced from ACP Journal Club.
Label/description Example
AN Accession number 1_: B2ND5C
& update - see Limit options -
TI Title 2_: BLOOD ADJ PRESSURE.TI.
SO Source* 3_: LANCET.SO.
or 4_: ARCH-DIS-CHILD$.SO.
AU Author(s)* 5_: DIXON-WOODS$.AU.
or 6_: QIZILBASH-N$.AU.
IN Author affiliation 7_: UNIVERSITY WITH HULL.IN.
FO funding organization 8_: LEEDS ADJ COMMUNITY.FO.
BI BMJ title 9_: CHILDREN WITH
RESPIRATORY.BI.
BS BMJ source 10_: EVIDENCE ADJ BASED ADJ
NURSING.BS.
EV Evaluation 11_: LUNG ADJ CANCER.EV
TX Text - synonym field for EV -
CR Cited references 12_: RANGANATHAN.CR.
DE MeSH headings* 13_: ATTITUDE-TO-HEALTH.DE.
or 14_: CARDIOVASCULAR ADJ
DISEASES.DE.
YR Publication year
YEAR= Publication year 15_: YEAR=2001
- see also Limit options -
PT Publication type
PT= Publication type 16_: PT=ARTICLE
..ROOT PT= for a list of available publication types
AT Article type
AT= Article type 17_: AT=AETIOLOGY
..ROOT AT= for a list of available article types
OC Occurrences - display only -
LE Length - display only -
CP Copyright statement 18_: BMJ ADJ PUBLISHING.CP.
(*) Phrases in these paragraphs can be searched using either
hyphens or the linking operators ADJ or WITH. The ROOT
command is especially useful here to establish, for example,
how a descriptor appears in the database.
1_: HIV
MONTH Publication month** 2_: ..L 1 MONTH < 200307
YEAR Publication year 3_: ..L 1 YEAR EQ 2001
UDATE Update date 4_: ..L UDATE > 20010713
UMONTH Update month 5_: ..L UMONTH WL
200312,200402
(**) The searchable publication month is that of the Evidence-
Based Journal rather than of the cited article. To
retrieve articles in the May 2002 quarterly edition of
Evidence-Based Mental Health, use the string 200205.
By paragraph - Title, Abstract _: ..P TI, AB 1-10
SHORT AN TI SO AU BI BS YR CP
MEDIUM AN TI SO AU IN FO BI BS EV CR YR CP
LONG AN TI SO AU IN FO BI BS EV CR DE YR PT AT CP
ALL AN TI SO AU IN FO BI BS EV CR DE YR PT AT OC LE CP
KWIC Context of search terms from the EV paragraph
FREE AN TI AU IN FO BI BS CR DE YR PT AT OC LE CP
_: ..P MED 1-3,5,7.
Duplication of articles:
Due to the subject matter of some of the original articles
evaluated, the same article may appear in more than one of the
Evidence-Based Journals. Note that though the articles
evaluated may be the same, the commentary may be different
depending on the perspective of the evaluator.
TI/SO - Original article title and source information:
Documents appearing in the Evidence-Based Journals cite articles
from other publications. The titles and source information of
these original articles will appear in TI and SO.
BI/BS - BMJ title and source information:
The title of the article as it appears in the Evidence-Based
Journal appears in BI; the source citation details of the
specific Evidence-Based Journal appear in BS.
Publication dates:
The publication year that appears in YR is that of the Evidence-
Based Journal (field: BS); it is not the publication year of the
article cited. To restrict retrieval to a particular edition of
a journal, use the ..LIMIT feature with the label MONTH (see
above). For example, to retrieve articles in the May 2002
quarterly edition of Evidence-Based Mental Health, use the
numerical string 200205.
To search publication years of the cited articles themselves,
qualify your search to the SO field, e.g.:
1_: 2002.SO.
For a complete guide to Evidence-Based Medical Journal search as
BASE-EBMJ in the BASE database.
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